1. Field of the Invention
The present invention relates to an OLED (organic light-emitting device) panel obtained by forming an OLED on a substrate and sealing the OLED between the substrate and a cover member. The invention also relates to an OLED module in which an IC including a controller, or the like, is mounted to the OLED panel. In this specification, ‘light-emitting device’ is the generic term for the OLED panel and for the OLED module. Electronic equipment using the light-emitting device is also included in the present invention.
2. Description of the Related Art
Being self-luminous, OLEDs eliminate the need for a backlight that is necessary in liquid crystal display devices (LCDs) and thus make it easy to manufacture thinner devices. Also, the self-luminous OLEDs are high in visibility and have no limit in terms of viewing angle. These are the reasons for attention that light-emitting devices using the OLEDs are receiving in recent years as display devices to replace CRTs and LCDs.
An OLED has a layer containing an organic compound (organic light-emitting material) that provides luminescence (electroluminescence) when an electric field is applied (the layer is hereinafter referred to as organic light-emitting layer), in addition to an anode layer and a cathode layer. Luminescence obtained from organic compounds is classified into light emission upon return to the base state from singlet excitation (fluorescence) and light emission upon return to the base state from triplet excitation (phosphorescence). A light-emitting device according to the present invention can use one or both types of the light emission.
In this specification, all the layers that are provided between an anode and a cathode together make an organic light emitting layer. Specifically, the organic light emitting layer includes a light emitting layer, a hole injection layer, an electron injection layer, a hole transporting layer, an electron transporting layer, etc. A basic structure of an OLED is a laminate of an anode, a light emitting layer, and a cathode layered in this order. The basic structure can be modified into a laminate of an anode, a hole injection layer, a light emitting layer, and a cathode layered in this order, or a laminate of an anode, a hole injection layer, a light emitting layer, an electron transporting layer, and a cathode layered in this order.
The problem in putting a light-emitting device using the OLED into practice is degradation of the device by heat, light, moisture, oxygen, and other causes.
When manufacturing a light-emitting device with OLED, in general, the OLED is formed after a wiring line and a semiconductor element are formed in a pixel portion. Once the OLED is formed, a first substrate on which the OLED is placed is bonded to a second substrate (made of metal or glass) for sealing (packaging) the OLED so that the OLED is not exposed to the outside air. A resin or the like is used to bond the substrates and nitrogen or inert gas fills the space between the substrates. However, oxygen easily reaches the OLED sealed as above by the substrates and a resin through the slightest crack in the package. Furthermore, moisture finds no difficulty in seeping into the OLED through the resin used in bonding and sealing. This causes non-light emission portions called dark spots, which grow larger with time and emit no light, which becomes a problem.